The Phase Linear 400 Guinea Pig

[laatsch55]

Do you want to simulate a blown fuse , or push and see if it goes?

 

[NavLinear]

Well yeah, right now. You're calling down changes and I'm makin em. It seems the only way to see if that was a cure is to duplicate the push.

R35 in. got a little rough with Q7R last time and ripped the base trace, thank goodness that doesn't see much. Managed to get a small sliver back in the hole and a good solid solder job.

It looks like you're out of transistor standoffs Lee. I'm guessing if I came up with more you'd use them?

 

[Gepetto]

Do you want to simulate a blown fuse , or push and see if it goes?

I would rather push it and see if it (what) goes Lee. You are the master of pushing things over the limit

 

[laatsch55]

No Dennis I'm fine there, had to leave that one out to fix a brooken trace I ripped when I got a little horsey with it. Should have sucked it one more time. And this board I put together before I got the standoffs.

 

[laatsch55]

I would rather push it and see if it (what) goes Lee. You are the master of pushing things over the limit

OK Dad, to the clip point we go...

 

[laatsch55]

I'm losing the positive rail fuse at 240 watts at 8 ohms. Did it twice. The minus rail fuse does not look stressed. It did not take out the pico fuse, either one.

 

[laatsch55]

Q10, Q5 running hotter than normal...both channels.

 

[Gepetto]

I'm losing the positive rail fuse at 240 watts at 8 ohms. Did it twice. The minus rail fuse does not look stressed. It did not take out the pico fuse, either one.

That looks like progress of a sort Lee. You wanna come halfway back on R35 to 10 ohms instead of 22? Was it a 5A AGX fuse on the topside that went?

 

[laatsch55]

No these are AGC, 5 amp. Going for 10 ohms.....

 

[Gepetto]

I'm losing the positive rail fuse at 240 watts at 8 ohms. Did it twice. The minus rail fuse does not look stressed. It did not take out the pico fuse, either one.

That is about spot on where a 5A fuse should blow Lee with you pulling 240W x 2 channels into 8 ohms.

 

[laatsch55]

Made it to just over 210 this time when something else gave. No pico fuse gone, no rail fuse gone. +5.632 vots DC on the speaker outs. Back o the bench...

 

[laatsch55]

I'm showing some leak between the C-E jct on Q7R/L. Let me get em pulled and checked.

 

[laatsch55]

Q 7's are fine...

 

[Gepetto]

Q 7's are fine...

Well that is a good sign Lee. Appears it does not take much negative feedback on the emitter of Q7 to tame the peak current.

 

[laatsch55]

Still haven't found the problem, got a funny acting R2, but I don't think that's it.

 

[laatsch55]

Gotta get up early tomorrow morning folks, nite.

 

[laatsch55]

The B+ rail fuse was blown.

 

[Gepetto]

The B+ rail fuse was blown.

So a pretty benign failure Lee. That is what we are working to get to. That is the goal of FMEA.

 

[laatsch55]

OKay, what now. 240 wasn't near it's potential...

 

[Northwinds]

That is about spot on where a 5A fuse should blow Lee with you pulling 240W x 2 channels into 8 ohms.

Joe, how the heck am I running 8A fuses and not destroying things inside then???? The amp's heat protections trip instead. I am lost on all this, I know I am pushing max power, needles are buried flat usually when I am playing my guitar along with it. Tweeter protections usually kick in before the heat protections trip though

I need me some edumacation